1. Field of the Invention
The present invention relates to a broadband mobile communication system, and more particularly to a method and apparatus for performing a carrier management procedure in a broadband wireless communication system supporting multiple carriers.
2. Discussion of the Related Art
A base station (BS) for use in a conventional wireless communication system includes a single PHY (physical layer) entity capable of supporting a single frequency channel (or a single carrier), and a single Medium Access Control (MAC) controller for controlling the single PHY entity may be provided to the base station (BS). In addition, a plurality of MAC-PHY entities may be present in a single cell. A mobile station (MS) that is capable of exchanging data with the base station (BS) by a single MAC-PHY entity during a certain transmission time interval (TTI), may be referred to as a single-carrier supported MS.
In recent times, a multi-carrier supported wireless communication system such as a multi-carrier aggregation has been proposed to allow the MS to exchange data with the BS through a plurality of carriers.
Multi-carrier aggregation technology achieves data communication between a mobile station (MS) and a base station (BS) through a plurality of aggregations of bandwidth-based carriers that are defined in a conventional wireless communication system (IEEE 802.16e in an IEEE 802.16m system or a Long Term Evolution (LTE) in a Long Term Evolution-Advanced (LTE-A) system). FIGS. 1(a) and 1(b) illustrate contiguous carrier aggregation and non-contiguous carrier aggregation, respectively.
In a multi-carrier supported system, a plurality of frequency channels may be controlled by a single common MAC as necessary. If the frequency channels are controlled by the single common MAC, some MAC messages transmitted via a single carrier can also be applied to other carriers.
Carriers associated with operations of a multi-carrier mode may be classified into a primary carrier and a secondary carrier. The primary carrier may allow the base station (BS) to exchange traffic and PHY/MAC control signaling (e.g., MAC control message) with the mobile station (MS). Although the multi-carrier supported MS is used, it can be defined that the multi-carrier supported MS has only one primary carrier as necessary. The secondary carrier is an additional carrier used by the mobile station (MS) for traffic, and may be used according to a specific command by the base station (BS) and rules that are received through the primary carrier.
MAC control messages for carrier management may be defined. For example, an Advanced Air Interface Carrier Management Command (AAI_CM-CMD) message and an Advanced Air Interface Carrier Management Indication (AAI_CM-IND) message are defined in an IEEE 802.16m standard specification. By the AAI_CM-CMD message received from the base station (BS), primary carrier change, secondary carrier management (secondary carrier activation and/or deactivation), and carrier switching may be performed. The AAI_CM-IND message is a MAC control message used as a response to the AAI_CM-CMD message, and is transmitted from the mobile station (MS) to the base station (BS).